How many lone pairs of electrons are present on the Br atom in BrF_5 according to its Lewis dot structure?

• A. 0
• B. 1
• C. 3
• D. 2

Answer: (B)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons for the bromine (Br) atom. Bromine is in group 17 of the periodic table, so it has 7 valence electrons.
2. Step 2: Recognize that in BrF_5, bromine is the central atom bonded to five fluorine atoms. Each Br–F bond uses 2 electrons (a bonding pair). Since there are 5 bonds, bromine uses 5 bonding pairs (10 electrons) in bonding.
3. Step 3: Calculate the total electrons around bromine by adding its valence electrons and the electrons it shares in bonds. Bromine starts with 7 valence electrons, but in bonding, it shares electrons with fluorine atoms.
4. Step 4: Use the octet rule and expanded octet concept. Bromine can have more than 8 electrons because it is in period 4. Count the bonding pairs (5 pairs) and subtract from the total valence electrons to find the remaining electrons as lone pairs.
5. Step 5: The remaining electrons on bromine that are not involved in bonding form lone pairs. Since bromine has 7 valence electrons and forms 5 bonds, the leftover electrons correspond to 1 lone pair on the bromine atom.